text: #!/usr/bin/env python
  
  import sys, re, operator, string, inspect
  
  #
  # The functions
  #
  def extract_words(path_to_file):
      """
      Takes a path to a file and returns the non-stop
      words, after properly removing nonalphanumeric chars
      and normalizing for lower case
      """
      if type(path_to_file) is not str or not path_to_file:
          return []
  
      try:
          with open(path_to_file) as f:
              str_data = f.read()
      except IOError as e:
          print "I/O error({0}) when opening {1}: {2}".format(e.errno, path_to_file, e.strerror)
          return []
      
      pattern = re.compile('[\W_]+')
      word_list = pattern.sub(' ', str_data).lower().split()
  
      try:
          with open('../stop_words.txt') as f:
              stop_words = f.read().split(',')
      except IOError as e:
          print "I/O error({0}) when opening ../stops_words.txt: {1}".format(e.errno, e.strerror)
          return []
  
      stop_words.extend(list(string.ascii_lowercase))
      return [w for w in word_list if not w in stop_words]
  
  def frequencies(word_list):
      """
      Takes a list of words and returns a dictionary associating
      words with frequencies of occurrence
      """
      if type(word_list) is not list or word_list == []:
          return {}
  
      word_freqs = {}
      for w in word_list:
          if w in word_freqs:
              word_freqs[w] += 1
          else:
              word_freqs[w] = 1
      return word_freqs
  
  def sort(word_freq):
      """
      Takes a dictionary of words and their frequencies
      and returns a list of pairs where the entries are
      sorted by frequency 
      """
      if type(word_freq) is not dict or word_freq == {}:
          return []
  
      return sorted(word_freq.iteritems(), key=operator.itemgetter(1), reverse=True)
  
  #
  # The main function
  #
  filename = sys.argv[1] if len(sys.argv) > 1 else "../input.txt"
  word_freqs = sort(frequencies(extract_words(filename)))
  
  for tf in word_freqs[0:25]:
      print tf[0], ' - ', tf[1]
  
  